Fuel composition



3,033,666 FUEL COMPOSETKQN Ned F. Walter, Nashville, Tenn, and Rolland M. Waters,

Freeport, and John M. Lee, Lake Jackson, Tern, assignors to The Dow Chemical Qompany, Midland, Mich, a corporation of Delaware No Drawing. Original application June 16, E58, er. No. 740,2!)1. Divided and this application Mar. 21, 1960, Ser. No. 13,216

4 Claims. (CI. 44-77) This invention relates to a new composition, 1-bromo- 2,2-dimethoxypropane, a method for its preparation, and a fuel composition for spark-ignition internal combustion engines containing the novel composition as an additament' to improve the performance characteristics of the fuel.

This application is a division of application Serial No.

. 746,2G1, dated June 16, 1958, now abandoned.

The new compound is a clear colorless liquid having a boiling point of .6 C. at millimeters of mercury pressure. It is useful as a fuel additament for spark ignition internal combustion engines to reduce the octane requirement increase of the engines using the fuel.

In recent years the manufacturers of automotive engines have steadily increased the compression ratio to increase the horsepower. This trend presents a serious problem to the petroleum industry in that the steady increase in compression ratios necessitates the production of a gasoline with higher octane rating for satisfactory antiknock performance. To meet the demands of the high compression engines, efforts have been directed primarily to the development of motor fuels with higher octane values. This has been largely accomplished by subjecting the gasoline type fuels to severe a hylation and by the use of additaments such as tetraethyl lead to raise the octane value of the fuel. It is known that in the operation or" an internal combustion engine deposits are formed in the combustion chamber of the engine and that an engine which has been used requires a fuel of higher octane rating than a new or clean engine in order not to knock. As a new or clean engine is used deposits form and the octane requirement increases until a point is reached where further use will not increase the octane requirement. Apparently, the deposits do not increase above a certain point or, if they do, the additional deposits do not affect the octane requirement characteristics of the engine. When this leveling off point is reached, the used or dirty engine may have an octane requirement of 6 or more numbers higher than a new or clean engine. In accordance with the invention, the addition of this new compound in the fuel reduces the increase in octane requirement of the engine when it is used or becomes dirty to about 2 to 3 octane numbers instead of 6 or more octane numbers. Thus, this enables the manufacturing and marketing of fuel of less octane number to give the required anti-knock performance.

The new compound may be prepared by the reaction of Z-methoxypropene with sodium methylate and bromine in 21 methanol solution at a temperature in the range of 20 to 50 0, preferably 28 to 30 C. The Z-methoxypropene may be intermixed with the sodium methylate in a methanol solution and a stoichiometric amount of bromine gradually added while cooling the reaction mixture to maintain the reaction temperature. The rate of reaction is relatively rapid and is substantially completed within 5 to 30 minutes after the addition of the bromine.

The product, l-bromo-2,2-dimethoxypropane, may be separated from the reaction mass by liquid-liquid extraction. The new compound is only slightly soluble in water so that upon contacting the reaction mass with water two phases are obtained with thenon-aqueous phase being substantially 1-bromo-2,2-dimethoxypropane. The 1-bromo 3,033,666 Patented May 8, 1962 2,2-dimethoxypropane layer may be fractionated under reduced pressure, such as 25 milliliters of mercury, to further purify it, if desired.

By adding a small amount of 1-bromo-2,2-dimethoxypropane to gasoline, a new fuel composition is prepared which will produce a much smaller octane requirement increase when the engine is operated on this fuel. The addition of a small amount of l-bromo-2,2-dimethoxypropane does not materially raise the octane rating of the fuel, but when the fuel is used in the engine, it decreases the tendency of the engine to knock due to the increase of octane requirement. Further preignition and autoignition are substantially reduced. Since most of the fuel is consumed by engines which have been used and would be considered dirty, the octane rating of the fuel marketed must have sufficient octane rating for anti-knock performance in these engines. Thus by using this additive, a fuel having an octane rating of around 3 octane numbers lower can be marketed and will give the required performance.

The term octane requirement, as used herein, means the minimum octane value of the fuel which will give knoclbfree performance in the engine and the term 0ctane requirement increase" means the increase in the octane requirement of an engine which occurs when a new or clean engine is used and deposits are formed in the combustion chamber thus requiring a fuel of higher octane number to give knock-free performance.

The gasoline in the composition may or may not contain other additaments. Gasolines used today for spark ignition internal combustion engines commonly are loaded,

that is they contain a lead alkyl anti-knock compound, such as tetraethyl lead, as an additament to raise the octane rating of the fuel. Gasolines may also contain additional additaments, such as volatile alkyl halides which are added to reduce the deposition of the combustion prodnets of the anti-knock compounds added, anti-oxidants, a dye, and other additaments. Thus, the term gasoline as used herein, means the hydrocarbon fuels normally employed in spark ignition engines which include the hydrocarbon fuels containing the normally used additaments. While the addition of 1-bromo-2,2-dimethoxypropane in gasolines which may or may not contain other additaments is effective in reducing the octane requirement increase of these fuels, it is especially effective in leaded gasolines. The octane requirement increase is much greater when an engine is operated wth leaded gasoline or gasoline containing tetraethyl lead than with unleaded gasolines. Thus the improvement obtained is much greater when the additament of the invention is used in this gasoline.v

Only a small amount of 1-bromo-2,2-dimethoxypropan is necessary to effectively reduce the octane requirement increase of an engine. The lower limit of the amount of additament used is generally around 1 milliliter per gallon of fuel, although smaller amounts may be used to obtain significant improvement in lowering the octane requirement increase. Amounts up to 20 milliliters per gallon may be used, but it is preferred to use from 2 to 8 milliliters per gallon. Concentrations over 20 milliliters per gallon, while not deleterious, are uneconomical. The additament is soluble in the gasoline and the new fuel composition can thus be easily prepared by mixing the desired amount of the additament in the gasoline.

In the following examples,,Example I illustrates in detail the preparation of the new compound, l-bromo- 2,2-dimethoxypropane, and Example II shows the decrease l in the octane requirement increase obtained using a gasoline containing the new compound as an additament.

Example I aoeaeea 3 were intermixed in a 1 liter flask. The flask was equipped with an agitator, a dropping funnel, a thermometer extending into the mixture in the flask, and a vent protected with a calcium chloride tube. The flask was placed in a salted ice bath and the contents cooled to about -l C. While the mixture was being agitated, one mole of bromine was added through the dropping funnel over a period of about 30 minutes. During the addition the contents of the flask were agitated and the temperature maintained at about C.

After the addition of the bromine, the flask was removed from the salt bath and its contents allowed to warm up to room temperature after which they were poured into 1 liter of water. Two phases were obtained with the nonaqueons phase containing most of the 1-bromo-2,2-dimethoxypropane. The aqueous phase was contacted with ether three times, using 150 mls. of fresh ether for each contact, to extract the 1-bromo-2,Z-dimethoxypro-v pane from the aqueous phase. The ether extract was dried over calcium chloride, and the ether stripped oif by distillation. The l-bromo-2,2-dimethoxypropane obtained after distilling oif the ether was combined with the portion separated initially which gave a yield of the product of about 86 percent.

Example ll In testing the new compound as an additament in gasoline, 1956 Buick automobile production model 8 cylinder V-8 internal gasoline engines were employed. These engines had an 8.5 to 1 compression ratio, a displacement of 324.3 cubic inches, a maximum horsepower of 202 at 4000 rpm, and a torque rating of 332 pounds per foot at 2400 r.p.m. The spark advance was 10.5 at 1200 r.p.m. and 22 at 2200 rpm. Prior to each test, each engine was completely dismantled, thoroughly cleaned, and all parts critically inspected. All parts that did not meet the measurements, tolerances, clearances, etc., specified by the Buick Service Manual were replaced. Each run was begun with a new set of spark plugs. The octane requirement for each engine was determined before the test and the data obtained in the'runs were corrected to a base octane requirement of 80.

The control fuel was 95 octane premium gasoline. This gasoline had an A.P.I. gravity of 59.45, a boiling range of 97 to 415 F., and contained from 2 to 2.4 milliliters of tetraethyl lead per gallon. The test fuel consisted of the control fuel to which was added l-oromo- 2,2-dimethoxypropane as an additament.

Two 100 hour test runs were made where one of the engines was operated on the control fuel and another of the engines was operated on the new fuel composition containing the additament. The octane requirements of the engines were determined after each hours of operation. At intervals of 20 hours the engines were shut down, the spark plugs carefully removed so as not to disturb any deposits, and a special set of spark plugs, reserved for rating during the particular run, were installed. Primary milliliters of tetraethyl lead per gallon.

reference fuels consisting of mixtures of n-heptane and iso-octane of varied octane number were supplied to the carburetor. The lowest octane number employed that did not produce audible knock was taken as a minimum octane requirement. Humidity and barometric pressure differences were corrected according to the standard methods. For every 30 grains of water above the standard humidity of grains per pound of dry air, a correction of one octane number was added to the observed value. The ratio of the barometric pressure to octane requirement is inversed so that for every increase of pressure of 0.3 inch of mercury above the standard barometric pressure of 29.92 inches of mercury, a correction of one octane number was subtracted. After the octane requirement of an engine was determined, the rating plugs were removed and discarded. The original spark plugs were replaced and the engine again operated.

The two runs were made using as the engine lubricant an SAE 10 W-30 multigrade petroleum base oil containing a polymethacrylate viscosity index improving compound.

The maximum octane requirement increase obtained in the hour test with the control fuel was 6.5 The engine operating on the fuel composition containing 4 The test fuel had an octane requirement increase of 3.4.. Thus, by using the additament in the fuel the octane requirement increase for the engines was reduced by around three octane. numbers.

What is claimed is:

1. A fuel composition for spark ignition internal combustion engines, which consists essentially of gasoline and a small amount of 1-bromo-2,Z-dimethoxypropane sufficient to decrease the octane requirement increase.

2. A fuel composition for spark ignition internal combustion engines, which consists essentially of gasoline and l-bromo-2,2-dimethoxypropane, said l-bromo2,2-dimethoxypropane being present in an amount less than 20 milliliters per gallon sufficient to decrease the octane requirement increase.

3. A fuel composition for spark ignition internal combustion engines, which consists essentially of gasoline and from 1 to 20 milliliters of l-bromo-2,2-dimethoxypropane per gallon.

4. A fuel composition for spark ignition internal combustion engines, which consists essentially of gasoline and from 2 to 8 milliliters of 1bromo-2,Z-dimethoxypropane per gallon.

References Cited in the tile of this patent UNITED STATES PATENTS 2,214,768 Lincoln Sept. 17, 1940 2,281,598 Prutton May 5, 1942 2,878,109 Wood et a1 Mar. 17, 1959 2,897,068 Pellegrini et a1 July 23, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,033,666 May 8, 1962 Ned F. Walter et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent shoultl read as corrected below.

Column 4, line 25, for "tetraethyl lead pergallon. The test fuel read l-br0mo2,2-dimethoxypropane per gallon Signed and sealed this 11th day of September 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A FUEL COMPOSITION FOR SPARK IGNITION INTERNAL COMBUSTION ENGINES, WHICH CONSISTS ESSENTIALLY OF GASOLINE AND A SMALL AMOUNT OF 1-BROMO-2,2-DIMETHOXYPROPANE SUFFICIENT TO DECREASE THE OCTANE REQUIREMENT INCREASE. 